1. Field of the Invention
This invention relates generally to semiconducting crystalline silicon and more particularly to the increase in the band gap of this material which can be produced by the treatment of normal crystalline silicon under very special processing conditions.
2. Description of the Prior Art
Crystalline semiconductor silicon has long been known, as has the chemical etching of this material, including the chemical etching of crystalline silicon so as to produce a material possessing a substantial porosity. Crystalline semiconductor silicon has always been considered to possess an electronic band gap of approximately one electron volt in width and this band-gap is often reported as 1.01 electron volts. However, it is also known that so-called hydrogenated amorphous silicon can have a band-gap which is wider than one electron volt and can even be as high as 1.3 electron volts. Such hydrogenated amorphous silicon is not crystalline, however, and therefore lacks many of the properties of crystalline silicon. Hydrogenated amorphous silicon can be produced by the glow discharge decomposition of silane or by the evaporation of silicon through a glow discharge containing hydrogen. However, bulk-like, interconnected porous crystalline silicon having a band-gap significantly above 1.01 electron volts has not previously been known and no method of producing it has previously been known.